Recently, a new type of retortable packaging suitable for in-container sterilization of foodstuffs was introduced. Referring to FIG. 1, a cross-section of this new packaging material 10 may be seen. The packaging material 10 is a generally flat sheet material that may include at least three layers, a core layer 14 generally composed of cardboard, and two outer layers 12 and 16 each composed of a polymer material. Additionally, packaging material 10 may include a gas barrier layer 18 that may be sealed or laminated to the core layer 14 by a layer of sealing agent 20. In one embodiment, a layer of binder or adhesive 22 may be used to bond the outer layer 16 to the gas barrier 18. In some embodiments, the outer layers 12 and 16 are formed from liquid-tight polymer coatings. Ink or printing 24 may be applied to the outside of the outer layers 16 or 12. Optionally, an additional protective layer (not shown) may be applied over the printing 24 to protect it. Packaging material 10 may include packaging materials generally similar to those disclosed in the following published PCT applications filed by TETRA LAVAL HOLDINGS & FINANCE S A, the disclosures of which are incorporated herein by reference: WO 97/02140 (PACKAGING LAMINATES BASED ON CARDBOARD AND PAPER); WO 02/22462 (A PACKAGING LAMINATE FOR A RETORTABLE PACKAGING CARTON); and WO 02/28637 (A PACKAGING LAMINATE FOR A RETORTABLE PACKAGING CONTAINER).
Packaging material 10 may be formed into packages by folding or creasing it into a desired shape. A sealing process may then be used to seal the edges or flaps together. In this manner, containers and/or packages may be formed in a variety of shapes and sizes.
As mentioned above, one of the exterior layers 12 or 16 of packaging material 10 may be suitable for printing 24. Information printed on packaging material 10 may include product related text such as the contents of the package, the brand name of the manufacturer, nutritional information, and/or instructions for use. Printed information may also include aesthetic and trade dress designs.
Packages formed from packaging material 10 may be considered “fragile” relative to packages formed from other materials such as metal or glass. Consequently, when handling, including clamping, and processing “fragile” packages constructed from packaging material 10 the strength and rigidity limitations of these packages must be taken into consideration. Generally, packages formed from packaging material 10 have a degree of rigidity that is satisfactory for some types of handling and transportation at ambient temperatures. However, in the case of in-package sterilization, the package may be exposed to temperatures of about 110–130° Celsius (240–266° F.). At sterilization temperatures, the mechanical characteristics of a package formed from packaging material 10 or similar packaging materials may change. Specifically, the package may experience decreased strength and/or increased pliability making handling the packages more difficult. Damage to a package may include dents, abrasion, deformation of the package, or any other undesirable change in the appearance of the package.
If the packages are exposed to water or steam during processing, the cut edges of the packaging material 10 may absorb moisture. Specifically, the porous fiber layer of the inner core layer 14 may be prone to absorbing moisture. The absorption of moisture by packaging material 10 may cause the layers to delaminate or become separated. Further, the packaging material may lose a degree of rigidity and strength if too much moisture is absorbed along its cut edges.
Because some products must be agitated in-package during processing, commercial retort apparatuses have been developed for this purpose. During agitation, packages must be held firmly to avoid scuffing and/or scratching of the printed information. However, the packages should not be held so firmly that they are damaged by the holding mechanism. Packages that have undergone sterilization or will undergo sterilization in conjunction with agitation may be more difficult to handle because their mechanical characteristics may become altered by the heat of the sterilization process.
Because containers formed from packaging material 10 and other packaging materials with similar properties may be unable to withstand the normal clamping load of stacking the packages atop one another to form a complete stack in an agitating retort, the packages may be arranged on independent trays. The independent trays are then arranged vertically on a carrier pallet. After the carrier pallet, including a stack of trays with packages placed between each adjacent pair of trays, is positioned within the retort drum, an upper clamping plate is lowered and clamped atop the stack. The carrier pallet may then be raised to clamp the stack firmly against the upper clamping plate. The trays may include upwardly extending side slats so that when the trays are stacked, the upwardly extending slats of the lower tray engage the upper tray. Between the upper and lower tray a volume is created into which the packages may be positioned. In this manner, the trays absorb the clamping load. Trays for use inside the drum of an agitating retort are well known in the art and do not require a detailed description.
While the trays may absorb a portion of the clamping load, the individual packages placed between the trays may move or shift relative to the trays during agitation within the drum of an agitating retort. Moving or shifting may result in damage to the packages including scuffing and scratching of the outer surface of the packages. Additionally, if the shifting of the packages is large enough, they may contact one another. If during rotation, the trays are angled causing the packages to shift toward one edge of the trays, the packages may bear against one another. If a sufficient amount of force is exerted on a particular package, it may become damaged or collapse. Particularly, if trays are rotated approximately 90° from horizontal, the packages may shift toward the lower edge of the tray and stack vertically upon one another. In this manner, the packages on the bottom of the stack may be exposed to the most force from the other packages in the stack making the bottom packages vulnerable to damage. Further, if shifting causes the packages to clump together, poor heat transfer to each package within the clump may result during sterilization. Therefore, a need exists for a package holder that is capable of retaining packages in a desired position during agitation in an agitating retort without damaging the packages. Particularly, a need exists for an apparatus capable of holding packages made from the new packaging material 10 and packaging materials with similar mechanical characteristics during processing (such as agitation within an agitating retort) and handling.
In addition to dimensional variation among the packages themselves, the trays may also contain variations in shape and size. Particularly, the trays may include manufacturing inaccuracies or other distortions due to repetitive use and/or handling. Some of this variation may result in trays of varying sizes or trays with an irregular package receiving surface. The package receiving surface is the portion of the tray that will receive at least one package for processing such as agitation and/or sterilization. Therefore, a need exists for a means of holding the packages in a desired position that is capable of coping with both the variation in the package dimension and the variation present in the trays. Similarly, a need exists for a device that provides a large deflection capability with minimal change in force applied to the package.